1. No trolling or spamming
2. First round is acceptance only
3. I will be assuming the "Pro" side (that is to say that I believe polygamy should be legal)
4. Be on topic, any arguments not pertaining to the discussion will be counted as an automatic forfeit.
5. Just to specify: "Polygamy" in this debate will refer to the marriage between 3 or more consenting adults to each other.

Thank you for accepting, and I hope to have a good and interesting debate!

REASON 1: THE LAW IS BASED ON CONSENT
Consent, v. To permit, approve, or agree; comply or yield (often followed by to or an infinitive): He consented to the proposal. We asked her permission, and she consented.
Most of international law, and all of United States law, is based on consent. The word is most often used in the context of sex. Here, we can see the obvious need for laws to be based around consent: if two parties are being affected by an action decided on by only one party, the rights of the other party are being intruded upon. As a result, we must ask ourselves: Why would we prevent consenting adults from partaking in an event that affects only those involved? As I defined previously, we are discussing legalizing only polygamy between consenting adults. This is because we have determined those under 18 not mature enough to be allowed to consent to marriage, as their brains are not developed enough to make such a decision. If this sounds like an argument for gay marriage, that"s because polygamy should be legalized for the exact same reasons. No one who is not a consenting adult will be harmed by the action of polygamy, and no one is being forced into it.
REASON 2: ILLEGAL POLYGAMY IS HARMING MANY
Like many drugs, the issue with making polygamy illegal is simply that the practice will continue unregulated. Many cases of polygamy occur regardless of whether they are legal or not. However, because the practice of polygamy was illegal, many unregulated instances of polygamy are occurring, and it is harming many. I doubt I even need to address the issue of child swapping, but if I must, we need look no further than the case of Ruby Jessop. According to Daily Mail UK, "Ruby Jessop was just 14-years-old when she was deemed "sexually mature" by polygamous sect leader Warren Jeffs and forced to marry her second cousin and step-brother and have sex with different men.
She was held against her will at the Fundamentalist Church of Jesus Christ of Latter Day Saints for the next 12 years, in which time she bore six children and lived under the iron first of their pervert leader"(Quigley, 2013)
This is a prime example of how unregulated polygamy can be a very dangerous thing. If this type of polygamy was being focused on by law enforcement, as opposed to the completely harmless marriages between consenting adults, surely this would lead to a better society for the United States. It may even encourage those who would otherwise participate in illegal behavior to be willing to be in safe, legal, polygamist marriages to avoid arrest.

I apologize for the rather small opening argument, but although I am on the "pro" side, most of the argument will naturally be you trying to prove that a legally monogamous society s superior, you do have the burden of proof. As such, I will mostly be focused on refuting your arguments against polygamy. I look forward to your rebuttal of my arguments as well as your own original positions.

You have forfeited the round, and according to customs on debate.org, I will give you the opportunity to continue the debate by giving your response here, else I will assume you have forfeited the debate.